RESUMO
Rec mutants of Bacillus subtilis have been tested for complementation by the recA gene of Proteus mirabilis (recApm) which was introduced into B. subtilis via the plasmid pHP334. In the recE4 mutant of B. subtilis the plasmid pHP334 restored significantly the defects in RecE functions tested: UV-sensitivity, homologous recombination (transduction and transformation) and prophage induction. Although serological methods to detect the presence of RecApm protein in B. subtilis have been unsuccessful, our results strongly indicate that the recE function of B. subtilis is analogous to the recA function of P. mirabilis.
Assuntos
Bacillus subtilis/genética , Proteínas de Escherichia coli , Exodesoxirribonucleases/genética , Genes Bacterianos , Proteus mirabilis/genética , Recombinases Rec A/genética , Bacteriófagos/genética , Regulação da Expressão Gênica , Plasmídeos , Recombinação Genética , Transdução Genética , Transformação BacterianaRESUMO
With the help of recombinant plasmids carrying the recA gene of Escherichia coli or of Proteus mirabilis the ability of the recA gene products to substitute functionally for each other was studied. The recA protein of each can function in recombination, repair, induction of mutations and prophages and in regulation of its own synthesis within the foreign host nearly equally well as in the natural host. It is, therefore, suggested that recA-dependent processes act similarly in E. coli and P. mirabilis.
Assuntos
Proteínas de Bactérias/genética , Escherichia coli/genética , Plasmídeos , Proteus mirabilis/genética , Recombinação Genética , Sobrevivência Celular/efeitos da radiação , Relação Dose-Resposta à Radiação , Escherichia coli/efeitos da radiação , Mutação , Proteus mirabilis/efeitos da radiação , Recombinases Rec A , Especificidade da Espécie , Raios Ultravioleta , Ativação ViralRESUMO
A gene of Proteus mirabilis that can substitute for functions of the recA gene of Escherichia coli has been cloned into the plasmid pBR322, using shotgun experiments. The recA-like gene (recAp.m.) has been localized by restriction mapping within a 1.5-Md PstI fragment that is a part of two cloned HindIII fragments of the chromosome of P. mirabilis. The restriction map of the recAp.m. gene differs from that of the recA gene of E. coli. Functionally, the recombinant plasmids containing the recAp.m. gene restore a nearly wild-type level of UV-resistance to several point and deletion mutants in the recA gene of E. coli.
Assuntos
Clonagem Molecular , Genes , Proteus mirabilis/genética , Recombinação Genética , Mapeamento Cromossômico , Enzimas de Restrição do DNA/metabolismo , DNA Bacteriano , Escherichia coli/genética , PlasmídeosRESUMO
In Proteus mirabilis nalidixic acid or a predose of UV induce Rec protein formation, a portion of post-UV replication repair and "post-UV replication enhancement." These inducible functions are not significantly affected by the plasmid R46, which renders P. mirabilis efficiently UV-mutable. The R46-mediated UV induction of rif mutations requires additional inducible functions, as existing after nalidixic acid treatment in rec+ strains. After a nalidixic acid pretreatment UV efficient induction of rif mutations occurs without an otherwise obligatory period of post-UV incubation prior to plating on rifampicin agar. THe inducible character of this "qualification" of plasmid R46-mediated UV mutagenesis in P. mirabilis is evident from the inhibitory effects of chloramphenicol and starvation. Constitutive high-level synthesis of Rec protein in cells harboring the recombinant (multi-copy) rec+ plasmid pPM1 reduced plasmid R46-mediated UV mutagenesis, probably by preventing (inducible?) functions required by the plasmid R46 repair-mutator.
Assuntos
Reparo do DNA , Mutação , Plasmídeos , Proteus mirabilis/genética , Ácido Nalidíxico/farmacologia , Fenótipo , Proteus mirabilis/efeitos da radiação , Raios UltravioletaRESUMO
E. coli K-12 and its lambda-lysogenic derivative were used to study the influence of lysogenic induction on the induction of mutants (streptomycin sensitivity to streptomycin resistance) by UV irradiation. The lambda-lysogenic strain responded to UV irradiation with increased sensitivity and with a strong reduction of the absolute mutant quantity, recovered per UV dose, as compared with the non-lysogenic parental strain. However, similar mutant freqqencies per surviving bacterium exclude the possibility that the diminished mutant recovery results from a selective killing of mutant cells by simultaneous induction of the processes of mutation and lysis.
